The invention concerns the field of avionics, specifically the providing of information to a pilot or flight crew and, potentially, to ground-based communications regarding the status of an aircraft.
Avionics devices generally available in modern aircraft range from instruments which had their technological origins in the first half of the twentieth century to more advanced, electronic- and computer-operated units. Regardless of their level of technological advancement, avionics devices characteristically accept information or data from a source and provide that information to the pilot either visually in raw form or in a translated (e.g., graphical) format that is more readily meaningful, or via a combination of visual and audio information.
These devices have historically been single-function units. That is, an avionics device will usually provide a single major piece of information. For example, a directional gyro indicates magnetic course, and tells the pilot nothing about airspeed, engine rpm, or oil temperature. Multi-function avionics devices were historically limited to a small set of functions, for example, a turn-and-bank coordinator provides a turn indicator and a slip-and-skid indicator.
One of the historical purposes served by an array of discrete devices is redundancy and, thus, overall systems reliability. For example, if the gyro in an artificial horizon failed in flight, that failure would not affect the operation of the airspeed indicator, the turn-and-bank coordinator, or the directional gyro, thus leaving the pilot without the artificial horizon but with an adequate instrument panel.
A further purpose in such discrete devices has been compensating for the variations in instruments needed for various airplanes. For example, the airspeed indicator for an aircraft may bear markings to indicate maximum flap extension speed, maneuvering speed, and never exceed speed. Because these speeds vary for different aircraft, combining other expensive instruments with the airspeed indicator would require manufacturing a variety of different models of the instrument package just to provide varied airspeed indications needed for various aircraft. Thus the cost of manufacturing and keeping inventory would rise, as would the cost to the aircraft owner to replace a device when only one component had failed.
The advent of reliable microelectronics and computers, as well as solid-state xe2x80x9cgyroscopesxe2x80x9d has changed the available instrumentation options. Electronic flight information systems, or xe2x80x9cEFIS,xe2x80x9d now combine a group of flight data displays into one or more displays for the pilot. These systems often combine information such as an artificial horizon display, directional gyro display, airspeed indicator, and vertical speed indicator into a single graphical display. Because they use electronic processors, these units can provide programmable indicators, such as for airspeed limitations, and can thus be programmed for use in a wide variety of airplanes.
However, EFIS does not eliminate the need for some redundancy for the purpose of safety. In a single-display EFIS, the failure of one critical component, such as a power-supply connection to the display, can eliminate all of the information the EFIS normally displays. Thus, safety concerns dictate that the airplane be equipped with some redundant, discrete instrumentation, which is expensive, or that the EFIS be manufactured to extreme reliability standards, which is also expensive. Costs for high-quality, FAA-approved EFIS units can be on the order of $50,000, and beyond the financial reach of many small airplane pilots. Indeed, the cost of such a unit exceeds the total value of many small airplanes.
Avionics devices also must be connected to an airplane to be of use. Depending on the avionics device, such connections may include: (1) condition inputs, such as ram- or static-air pressure, outside air temperature, oil pressure, and the like; (2) signal inputs, such as antenna feeds for communications and navigation radios; and (3) controls from the pilot, such as frequency changes or changes to trim settings. Further, a device may require additional connections, supplying such needs as power to operate, power to operate built-in lighting (usually from a dimmer circuit), or a source of positive or negative (vacuum) air pressure. Power connections must often be routed through switches and circuit breakers. Thus, the xe2x80x9cbehind-the-panelxe2x80x9d wiring and connections for an airplanes avionics is complicated, often messy in appearance, and expensive to repair or replace.
Further, avionics devices cannot always be flexibly arranged on an aircraft panel. Once the original holes are set in the panel, instrument positions are somewhat fixed. Even though many devices conform to xe2x80x9cstandardxe2x80x9d sizes, a 3xc2xd-inch device cannot be moved into a 2xc2xc-inch instrument hole, even if wiring and other connections could be moved. Similarly, radio widths and heights follow xe2x80x9cstandardsxe2x80x9d which change with function, the manufacturer, and the ever-advancing level of technology, which allows smaller devices to do more than their predecessors.
Accordingly, it is desirable to provide an avionics system which simultaneously overcomes many of the limitations of the current state of the art. It is an object of the present invention to provide a device and method for providing avionics information to a pilot which is reliable, allows continued operation in the event of the failure of one, or even multiple, components, reduces interconnection complexity, allows easy replacement or upgrade of individual components, and allows for flexibility in display arrangement.
It is a further object of this invention to reduce manufacturing costs, and thus retail costs, for avionics devices, and to allow greater flexibility in selecting avionics components for installation in a particular airplane.
The present invention comprises an information bus, which is intended to provide a set or subset of sensor information to each avionics device. For purposes of this invention, xe2x80x9csensorxe2x80x9d includes all forms of devices intended to collect information from the environment, or from the airplane itself. Thus, xe2x80x9csensor,xe2x80x9d as used herein, includes, but is not limited to: pilot tubes; static air pressure sensors; fuel gauges; oil pressure sensors; oil temperature sensors; water pressure sensors; water temperature sensors fuel pressure sensors; fuel, water, or oil flow sensors; thermocouples; cylinder head temperature sensors; exhaust gas temperature sensors; engine rotation rate sensors; electrical voltage sensors; electrical current sensors; trim position sensors; antennas, such as communication, navigation, and transponder antennas; air or vacuum pressure sensors; and gyroscopic or rotational position sensors. As those of skill in the art will recognize, not all of these sensors will exist on every airplane. Further, it may be desirable to provide redundancy for some sensors, such as gyroscopes, so that all flight instruments which depend on gyroscopic information from the bus will not become non-functional as the result of failure of a single gyroscope.
In many applications it will be desirable to digitize information which is collected in analog form by a sensor, and making the digitized information available on the bus. For example, it may be desirable to use a pressure transducer to create an electronic signal corresponding to the ram air pressure, and providing the electronic signal to the bus. However, doing so is not critical, although digitizing such information will likely be the most cost-efficient approach.
Further, separate information lines are not required on the bus for every sensor output; such signals may be multiplexed if desired. Moreover, not all of the sensor information needs to be available at every location on the bus. For example, it may be desirable to separate one section of the bus carrying radio signals from another section, to prevent interference with radio operations from other devices, or vice versa. Alternatively, antenna feeds may be removed from the bus altogether, and directed solely to computation devices which perform appropriate communication or navigation radio functions.
Computation devices are interconnectable with the bus in a manner which allows information to pass from the bus to each computation device, and vice versa. Each computation device generates secondary information corresponding to one or more avionics functions. Thus, as used herein, xe2x80x9ccomputation devicexe2x80x9d means a device which performs an avionics function based on an available piece or set of information. Accordingly, as used herein, computation devices include devices which perform the function of attitude instruments, engine instruments, communications and navigation radios, or other instruments and indicators, and which provide information to the pilot or flight crew or allow or assist the pilot or flight crew to perform their functions.
Those of skill in the art will recognize that multiple avionics functions can be performed by a single computation device. Although some functions will doubtlessly be so combined in various instantiations of this invention to allow for more efficient displays, this invention also provides for multiple individual instruments, allowing greater flexibility in the event of failure, lower repair cost, and greater flexibility for the aircraft owner in selecting which avionics instruments to install in his airplane.
The computation devices comprise printed circuit boards, similar to those found in desktop computers. Accordingly, each printed circuit board can be connected to the information bus by inserting a tabbed edge into a socket connected to the information bus, thereby allowing individual computation devices to be quickly installed, replaced, or removed from the airplane. Thus, new avionics devices can be quickly added, failed components replaced, or upgraded devices quickly installed. Those of skill in the art will recognize that it is desirable to mount the information bus in a rack or similar unit, to allow the use of edge guides and locking devices to insure that the printed circuit boards are correctly positioned, secured in place, and protected from damage due to vibration or other movement of the aircraft.
In the preferred embodiment, a secondary bus will comprise power supply circuitry, and the printed circuit boards will comprise edge connectors configured to attach the boards to the appropriate power circuit. In this way, switching circuitry, such as that used to turn power on or off to devices attached to the avionics master power switch, can be greatly simplified.
The secondary information generated by the computation devices is presented to the pilot or flight deck crew by electronically generating a visual display on a display device in analog, digital, or a combined analog-digital format. The generation of the visual display information is preferably transmitted to the display device via a standardized cable. As used herein, a xe2x80x9cstandardized cablexe2x80x9d is one which has the same pin-out specification as other such cables in the avionics system. Thus, if a display unit for a more critical flight instrument fails, the standardized cables can be exchanged between the failed display unit and a display unit which is being used for a less critical flight instrument, thus salvaging the function of the more needed flight instrument.
The display units will preferably be liquid crystal displays, and will also preferably be TFT displays or of equal or better resolution and clarity. Such displays provide low power usage, clarity, visibility in direct sunlight conditions, and can also provide color capability. However, other display types can suffice for use as display units as contemplated in this invention.
As with any avionics system, there will be some variation in actual display sizes used. For example, radio functions are more likely to be displayed on a rectangular display, with the longer axis disposed horizontally, if only to mimic the current radio faceplates to which most pilots are accustomed. Conversely, standard flight instruments such as an artificial horizon or directional gyro are more likely to be displayed on a square or rectangular display which mimics a standard 3xc2xd-inch device. Flight instruments for which information can be displayed on a smaller scale, such as fuel gauges or trim tab position indicators, could be displayed on a square or rectangular display which mimics a 2xc2xc-inch device, to save valuable panel space. However, the use of standardized cables means that information which is displayable at 2xc2xc-inches is also displayable at 3xc2xd-inches, and, within readability limits, vice versa. Further, those of skill in the art will recognize that, because the display units can transmit information via the standardized cable as well as receiving it, information regarding the display size can be provided automatically, and the display generator can adjust under software control to the actual display size in use. Even if three sizes of display units are used, this invention allows the efficient replacement of any one display unit, in the event of failure, by maintaining a stock of only three spares, one for each size in use.
Because the display units involved will be relatively flat and lightweight, they can be readily positioned on the avionics panel by means of set screws. Thus, a matrix of threaded holes set into an avionics panel can allow rapid and easy repositioning of any display unit, so that the pilot or flight crew will no longer be locked in to whatever panel layout was initially drilled. Further, the addition or removal of any avionics device will no longer require the creation of a new hole in the panel or open gap therein. Given sufficiently strong adhesives to secure the appropriate tape, the display units can alternatively be affixed to the avionics panel with a tape adhesive, such as VELCRO(copyright), allowing the rapid repositioning of any display unit.
In the preferred embodiment, the display units further comprise touch screen capability, so that displays can be generated which allow the pilot or flight crew to adjust the setting of the flight instrument. Thus, via direct electronic control, the pilot or flight crew can select functions displayed on the display unit to, for example, change frequencies on a communications or navigation radio, adjust the directional gyro display for drift, or adjust the altimeter setting. This information, transmitted via the standardized cable from the display unit to the computation device, can be used to update the state of the computation device and thus the display unit. Further, this information can be provided to the bus through the use of additional data lines, allowing every computation device on the bus effectively simultaneous access to the information provided by the pilot or flight crew.
As those of skill in the art will recognize, instead of touch screens, the display units can be supplemented as necessary with hardware such as selector knobs, buttons, and the like without departing from this invention. However, doing so imposes additional penalties of cost, incompatibility, and loss of redundancy which are to be avoided, if possible.
It will further be understood that a computation device may have links to multiple display units. Such situations will necessarily be the case if a computation device is designed to perform a function such as that provided by a traditional navigation radio, which would require one display unit to serve as the traditional radio faceplate and a second display unit to serve as the indicator. Further, a multi-function computation device might provide secondary information to multiple display units, rather than combining all of the displays into a single unit.
This invention overcomes many of the problems inherent with current avionics systems. The modularity involved allows various avionics to be quickly added or removed from an airplane without affecting the functioning of any other avionics function. Further, upgraded radios, global positioning systems, or other avionics can be installed without paying for, or installing, new displays. Displays can be moved, removed, replaced, or repaired without the cost of an attached avionics system. Further, the ready availability of flight sensor data on the bus allows for advances in flight safety, such as the ability to automatically transmit encoded forms of all available sensor data in an emergency. Thus, this invention, in conjunction with the appropriate software and hardware, could provide a xe2x80x9cpoor man""s black boxxe2x80x9d for aviation, and allow accident investigators unprecedented access to enhanced information.